The disappearance of the passenger jet is one of the biggest aviation mysteries since pilot Amelia Earhart and her navigator, Fred Noonan, disappeared over the Pacific Ocean on July 2, 1937, as they were attempting to circumnavigate the globe.

The Malaysia Airlines jetliner — which carried 239 people, most of them from China — lost contact with air traffic controllers less than an hour into the flight on March 7, 2014. The Boeing 777 aircraft was on its way to China from Kuala Lumpur.

Only a few pieces of debris have been found. Australia led a joint search that also involved China and Malaysia until January 2017.

MANAN VATSYAYANA via Getty Images
A young girl holds a balloon with a message during a memorial event for the missing Malaysia Airlines flight MH370.

A year later, the Malaysian government signed a contract with Ocean Infinity, a private U.S. company that specializes in collecting high-resolution seabed data, to search for wreckage of the missing plane. Under terms of the contract, Malaysia does not have to pay the company if wreckage or black boxes are not found. The contract has been extended twice, but Loke said Wednesday that it would not be extended past May 29.

Australia’s minister for infrastructure and transport, Darren Chester, estimates that the search has cost $151 million, with most of the expense being paid by Malaysia, according to CNN. The search is said to be the largest hunt for a missing plane in history.

While there are competing theories about what may have happened to the flight, no evidence has definitively settled the debate.

Earlier this month, the Australian version of “60 Minutes” aired a report suggesting that the pilot of the plane had deliberately crashed it into the Indian Ocean because he was despondent over the breakup of his marriage.

In October, the Australian Transport Safety Bureau released a 440-page report, noting “it is almost inconceivable and certainly societally unacceptable in the modern aviation era ... for a large commercial aircraft to be missing and for the world not to know with certainty what became of the aircraft and those on board.”